Are Ultra-Processed Foods Sneaking Fat Into Your Muscles?

A new study shines a light on a surprising culprit behind a hidden health risk: ultra-processed foods. Presented at the Radiological Society of North America’s annual meeting, the research links these popular convenience foods to higher fat storage in thigh muscles—a potential precursor to knee osteoarthritis. What’s more, this connection holds true regardless of calorie intake or exercise levels.

Ultra-processed foods, ranging from packaged snacks and soft drinks to frozen pizzas and energy bars, are everywhere. These items are often packed with artificial additives, engineered to last longer and taste irresistibly good. But their convenience could come at a significant cost to your health.

What the study found

Researchers analyzed data from 666 adults with an average age of 60 who participated in the Osteoarthritis Initiative, a long-term research project supported by the National Institutes of Health. On average, participants consumed diets where 40 percent of their foods were ultra-processed.

Unsplash

“The novelty of this study is that it investigates the impact of diet quality, specifically the role of ultra-processed foods in relation to intramuscular fat in the thigh muscles assessed by MRI,” Zehra Akkaya, MD, lead author and researcher in radiology at the University of California, San Francisco, said in a statement. “This is the first imaging study looking into the relationship between MRI-based skeletal muscle quality and quality of diet.”

The findings were striking: people who ate more ultra-processed foods had significantly higher levels of intramuscular fat in their thighs. This was true even when researchers accounted for factors like body mass index (BMI), caloric intake, and physical activity levels.

Why muscle fat matters

While many of us focus on visible fat, hidden fat in your muscles can have serious health implications. Fatty degeneration in muscles, where fat infiltrates muscle fibers, can reduce muscle strength and mobility. “Research from our group and others has previously shown that quantitative and functional decline in thigh muscles is potentially associated with onset and progression of knee osteoarthritis,”  Akkaya explained. This type of degeneration can be detected via MRI scans, offering a clear view of muscle quality.

Canva

RELATED: 11 Food Lessons From the Oldest People on the Planet

Osteoarthritis, which affects millions worldwide, is one of the leading drivers of healthcare costs in the US. It is strongly linked to obesity and poor lifestyle habits, including diet.

The convenience trap

Why are ultra-processed foods so hard to resist? These products are engineered for maximum palatability, often combining sugar, fat, salt, and refined carbs to trigger your brain’s reward system. Think about the last time you reached for a bag of chips or a sugary cereal—it’s not just about hunger; it’s the addictive blend of flavors that keeps you coming back for more.

Cottonbro Studio | Pexels

Ultra-processed foods are not just bad for your waistline; this study shows they can infiltrate your muscles as well. “In an adult population at risk for but without knee or hip osteoarthritis, consuming ultra-processed foods is linked to increased fat within the thigh muscles,” Akkaya said.

How to protect your muscle health

For those looking to avoid the risks, focusing on whole, minimally processed foods may be a game-changer. This means choosing fresh fruits and vegetables, whole grains, nuts, seeds, and lean proteins over pre-packaged meals and snacks.

Pexels

Preventing obesity through a healthy diet and regular exercise remains the gold standard for avoiding osteoarthritis and its complications. Beyond weight management, the quality of your diet matters deeply. “Understanding this relationship could have important clinical implications, as it offers a new perspective on how diet quality affects musculoskeletal health,” Akkaya said.

What this means for you

If your grocery cart is heavy on the boxed, bagged, and frozen, it may be time to rethink your choices. While the convenience of ultra-processed foods is appealing, their hidden effects on your muscles and joints are not.

Adobe

This study adds to growing evidence of the health risks associated with ultra-processed foods. A review in The BMJ linked these foods to heart disease and early mortality, while other research has associated them with low muscle mass and conditions like sarcopenia. Reducing your intake of these foods could benefit your overall health—and now, your muscle health, too.